/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hive.ql.optimizer.calcite.rules.views;

import org.apache.calcite.rex.RexBuilder;
import org.apache.calcite.rex.RexInputRef;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.rex.RexShuttle;
import org.apache.calcite.tools.RelBuilder;

/**
 * Shift input reference index by the specified amount (shift) if the referenced column index is higher or equals with
 * the startIndex.
 */
public class InputRefShifter extends RexShuttle {
  private final int startIndex;
  private final int shift;
  private final RelBuilder relBuilder;

  InputRefShifter(int startIndex, int shift, RelBuilder relBuilder) {
    this.startIndex = startIndex;
    this.shift = shift;
    this.relBuilder = relBuilder;
  }

  @Override
  public RexNode visitInputRef(RexInputRef inputRef) {
    if (inputRef.getIndex() >= startIndex) {
      RexBuilder rexBuilder = relBuilder.getRexBuilder();
      return rexBuilder.makeInputRef(inputRef.getType(), inputRef.getIndex() + shift);
    }
    return inputRef;
  }
}
